| Created: 10/24/95 |
Updated: 4/18/97 |
Project Number: C96-31
Experimental Degradation Analysis of Stored PEMs
Point of Contact: Dr. Michael Pecht
email: pecht@calce.umd.edu
Phone: (301) 405-5323
Fax: (301) 314-9269
Objective
Characterize the failure modes, failure sites, failure mechanisms and the
extent of degradation in PEMs stored for extended periods of time. Use
these results together with physics-of- failure acceleration transforms
for the dominant failure mechanisms and the results of accelerated testing
to assess the capability for even longer term reliability.
Background
Many complex electronic systems are required to operate reliably for many
years, which often requires using stored PEMs as replacement parts. This
combined with an increasing use of PEMs in applications requiring long
term dormant storage makes it important to assess the long term reliability
of stored PEMs.
A process has been developed to provide such an assessment of remaining
life. This process is based on the characterization of degradation in the
PEMs, together with the use of accelerated testing to simulate additional
field exposure, and the use of physics of failure based acceleration transforms
to relate the testing to actual "remaining life" in particular future use
and storage environments.
Approach
Stored PEMs will be characterized for degradation as follows:
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Visual and optical microscopic examination are made of the parts to identify
obvious sites of corrosion or external cracks.
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Electrical testing on both new and old parts is performed to identify sites
at which shorts, opens, or parametric shifts have occurred.
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PEMs are examined for delamination and cracking at the package interfaces,
and die attach voiding, by scanning acoustic microscopy.
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PEMs are de-encapsulated and examined by optical microscopy for
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wire fatigue or fracture
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die cracking or fracture
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PEMs are examined by E-SEM for evidence of:
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corrosion of the bond pads
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cracking of the passivation
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ball bond cracking or bond lift
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stress driven diffusive voiding
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metallization corrosion
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PEMs are cross-sectioned and examined for intermetallic growth at wire
bonds and leads by E-SEM.
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The composition of any corrosion products on the metallization, at the
bond pad, are identified by EDS.
Work Accomplished
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Generated report on the Analysis and Evaluation of Long Term Storage Stresses
